PostgreSQL – COUNT Function
PostgreSQL COUNT function is the simplest function and very useful in counting the number of records, which are expected to be returned by a SELECT statement.
To understand the COUNT function, consider the table COMPANY having records as follows −
testdb# select * from COMPANY; id | name | age | address | salary ----+-------+-----+-----------+-------- 1 | Paul | 32 | California| 20000 2 | Allen | 25 | Texas | 15000 3 | Teddy | 23 | Norway | 20000 4 | Mark | 25 | Rich-Mond | 65000 5 | David | 27 | Texas | 85000 6 | Kim | 22 | South-Hall| 45000 7 | James | 24 | Houston | 10000 (7 rows)
Now, based on the above table, suppose you want to count the total number of rows in this table, then you can do it as follows −
testdb=# SELECT COUNT(*) FROM COMPANY ;
The above given PostgreSQL statement will produce the following result −
count ------- 7 (1 row)
Similarly, you want to count the number of records for Paul, then it can be done as follows −
testdb=# SELECT COUNT(*) FROM COMPANY WHERE name='Paul';
count ------- 1 (1 row)
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- Theoretical Machine Learning: This is about math and abstraction and idealized scenarios and limits and beauty and informing what is possible. It is a whole lot neater and cleaner and removed from the mess of reality.
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